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for Mixed Contention/Cut-Through
Marat Zhanikeev [email protected] maratishe.github.io
2016/11/18@PN研@KDDI研
The Switchboard
PDF: bit.do/161118
Traffic Engineering Problem
#STEP #TE #TrafficEngineering #OSPF #cut-through #contention #SDN Output Channels
.
Commutators are Back (as robots)• all the technology is already there, we just need to start using it• basically, switching robotics
◦ this paper proposed the Switchboard Traffic Engineering Problem(STEP)
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Cut-Through Mode as Basis for STEP
C: Cut Through
Check, etc. Q: Queue
D: DropQoSclasses
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STEP (1)• each outgoing port gets multiple slots, i.e. the n-by-m switchboard• can be implemented as multiple ethernet ports, fiber wavelengths, etc.
A switch 4-port switchPhysical Logical Switchboard
n×mswitchingmatrix
xth port,y slots n ports
m slots
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STEP (2) The Weight Setting Problem• 1st element: weights per slot, the same way as in the OSPF problem
• 2nd element: migrations of some slots to other outgoing ports
Switchboard
n×mswitchingmatrix
n portsm slots
Occupied/used slotEmpty slot
Migration(1:3 to 3:2)
w11 w21
wnm
wn1………
Weight setting
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Formulations (1) OSPF Cases
• unit demand as source s, destination d, volume v, time t, and sometimes opticalwavelength λ, can be written as Ti = ⟨s, d, v, t⟩
• traditional/OSPF : Ti = ⟨s, d, v⟩ → ⟨s, a, b, ..., d⟩• optimal w/out switching : Ti = ⟨s, d, v⟩ → ⟨s, λ⟩• optical with switching : Ti = ⟨s, d, v⟩ → ⟨s, λs, λa, λb, ...⟩• e2e circuits : Ti = ⟨s, d, v, t1, t2⟩ → ⟨s, λ, t⟩
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Formulations (2) The STEP Problem
• M load spread across n outgoing ports, each with m slots (n-by-m switchboard)
◦ unit of load is flowsize vi• load aggregated per slot xy : Lxy = max
{vi}xy, i ∈ xy
• fitness of the slot xy : Fxy = wxyLxy
• aggregate slots into ports as potential : Px =∑{Fj
Vj
}y, j ∈ x
• optimize (w/out migrations) : minimize max{P}xsubject of x ≤ n
• optimize (with migrations) : minimize a · max{P}x+ (1− a) ·
∑i∈m Ci
◦ .... subject of x ≤ n, a ≤ 1, m ≤ Q.
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Experiment (1) Setup
0 20 40 60 80 100Decreasing order
0
0.35
0.7
1.05
1.4
1.75
2.1
2.45
2.8
log(
val
ue)
Class AClass BClass CClass DClass E • hotspot distributions for
picking weights -- same asin OSPF, (i.e. large flows repel other flows)
• use WIDE packet traces forreal packets/flows
• otherwise, the same as inOSPF -- just optimize theweights
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Experiment (2) Results
0 1 2 3 4 5 6
X (port) + Y (slot) coordinate
9560
9600
9640
9680
9720
9760
9800
Load
ind
ex (l
og o
f hot
spot
)
1
1
1
2 2
2
3
3
3
44 4
5
5
5
1
1
1
2 2
2
3
3
3
44 4
5
5
5
Method : real
0 1 2 3 4 5 6
X (port) + Y (slot) coordinate
9560
9600
9640
9680
9720
9760
9800
Load
ind
ex (l
og o
f hot
spot
)
1
1
1
1
1
2
2
2
3
3
3
4
4
4
51
1
1
2
22
3
3
3
3
34
4
4
5
Method : optimal
Hotspot class : D
• real = based on real traces and notoptimized
• optimal is the optimized version ofthe switchboard
• visual effect: STEP spreads thetraffic across ports
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Experiment (3) Layouts (good)
0 2 4 6 8 10 12 14Decreasing order
0
2
4
6
8
10
log(
1 +
fitn
ess)
beforebefore#10.6hotclass#Emigrations#5
10.4
0
2.5
10
10.5
3.1
0
0
10.6
10.4
0
3.1
9.9
10.1
7.8
before
0 5 10 15 20 25Decreasing order
0
2
4
6
8
10
log(
1 +
fitn
ess)
afterafter#10.6 (diff#-0.1)hotclass#Emigrations#5
10.40
2.5010
00
3.10
10.4
00
10.600
0000
10.5
9.910.17.80
3.1
after
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Experiment (4) Layouts (bad)
0 2 4 6 8 10 12 14Decreasing order
0
2
4
6
8
10
log(
1 +
fitn
ess)
beforebefore#10.7
6.2
10
6.7
8.6
9.3
9.3
9.8
0
5.7
0
0
10.7
0
0
9.8
before
0 5 10 15 20 25Decreasing order
0
2
4
6
8
10
log(
1 +
fitn
ess)
afterafter#10.7 (diff#0)
6.2106.700
8.69.39.300
00
5.700
00
10.700
00
9.89.80
after
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Summary
• cut-through circuits are possible even under a large number of flows
• will work with 2+ independent outgoing ports• future steps: actually build a switching robot
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That’s all, thank you ...
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STEP is NOT a scheduling problem
Line =
outgoing
port
Overhead = contention
No. of flows
Line =
outgoing
port
Overhead
Scheduling
Traditional
Circuits
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Future NOC...
• ... will manage a pool of packet and circuit ports
NOC
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STEP in the Hotspot Context• version 1: map all heavy hitter flows as circuits• version 2: offer a paid service that some of the bulk transfer services canuse
ezis wolF
Decreasing flow size
TopNparameter
In Out
Switch
CircuitsPackets
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